STARTTLS protocol probe

Inspect TLS on STARTTLS services; swap postgres for smtp/imap/mysql/ldap

openssl s_client -connect <host>:5432 -starttls postgres -showcerts </dev/null 2>/dev/null
tool
openssl27 commands
tags
openssltlsnetworkdebug

More openssl commands

  • Generate Ed25519 key
    openssl genpkey -algorithm ed25519 -out ed25519.pem

    Modern: Ed25519 keys are tiny and fast vs RSA; use for signing/mTLS

  • Test specific TLS protocol
    openssl s_client -connect <host>:443 -tls1_2 </dev/null 2>&1 | grep -E 'Protocol|Cipher'

    Force a version to confirm support; use -tls1_3 / -no_tls1_2 to test policy

  • Generate RSA private key
    openssl genrsa -out private.key 4096

    Generate a 4096-bit RSA private key

  • Generate Ed25519 key pair
    openssl genpkey -algorithm ed25519 -out private.key && openssl pkey -in private.key -pubout -out public.key

    Modern Ed25519 key (smaller, faster than RSA)

  • Create CSR
    openssl req -new -key private.key -out request.csr -subj '/CN=example.com/O=MyOrg/C=RU'

    Certificate Signing Request for CA submission

all 27 openssl commands